Vehicular drive system

ABSTRACT

A second electric motor is arranged on a first axis on which an output shaft of the engine is arranged, a transmission is arranged on a second axis which is parallel with the first axis, and a clutch is arranged on the first axis to selectively connect and disconnect the second electric motor and the transmission to and from the engine. Power on the first axis is transmitted to an input shaft of the transmission via a power transmitting mechanism.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2004-329201 filed onNov. 12, 2004 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a vehicular drive system which is used in avehicle such as an automobile.

2. Description of the Related Art

A vehicular drive system is known which includes an engine, two electricmotors, a transmission, and a clutch that is operatively connected tothe engine and can selectively connect and disconnect the transmissionto and from the engine. One example of such a vehicular drive system isdisclosed in US Patent Application Publication No. 2003/0127262A1. Inthis type of vehicular drive system, the clutch is provided in place ofa fluid power transmitting device such as a torque converter, and thetransmission shifts speeds while an input shaft thereof is operativelyconnected to the engine via the clutch.

With the vehicular drive system disclosed in US Patent ApplicationPublication No. 2003/0127262A1, the omission of a torque converterenables the overall length to be made shorter. Despite this, however,the engine, the two electric motors, the clutch, and the transmissionare all arranged on the same axis, which makes the overall length long.Thus, while it is possible to mount this vehicular drive systemlongitudinally in a FR (front-engine-rear-drive) vehicle, it isdifficult to mount transversely in a FF (front-engine-front-drive)vehicle or a RR (rear-engine-rear-drive) vehicle. That is, this type ofdrive system may be difficult to mount when mounted with its axialdirection parallel to the wheel axles. In addition, the drive system mayalso be difficult to mount longitudinally if the mounting space islimited.

SUMMARY OF THE INVENTION

In view of the foregoing circumstances, this invention thus aims toprovide a vehicular drive system, the dimensions of which can beshortened in the transverse direction when the drive system istransverse mounted, i.e., in the axial direction.

Therefore, a first aspect of the invention relates to a vehicular drivesystem including an engine, a first electric motor, a second electricmotor that is arranged on a first axis on which an output shaft of theengine is arranged, a transmission that is arranged on a second axiswhich is parallel with the first axis, and a clutch that is arranged onthe first axis and can selectively connect and disconnect the secondelectric motor and the transmission to and from the engine, thetransmission being arranged parallel to the engine and the clutch, andpower transmitting means for transmitting power on the first axis to aninput shaft of the transmission.

According to this structure, the clutch and the second electric motorare arranged on the first axis on which the output shaft of the engineis arranged, the transmission is arranged on the second axis which isdifferent from the first axis, and the engine and the clutch on thefirst axis and the transmission on the second axis are parallel witheach other. As a result, the dimensions in the transverse direction,i.e., the axial direction, of the vehicular drive system are able to beshortened.

Further, in the foregoing vehicular drive system according to the firstaspect of the invention, the first electric motor may be arranged on thefirst axis.

According to the this structure, the first electric motor is alsoarranged on a different shaft than that of the transmission. As aresult, the dimensions in the transverse direction, i.e., the axialdirection, of the vehicular drive system are able to be shortened evenmore.

Further, in the foregoing vehicular drive system according to the firstaspect of the invention, the clutch may be arranged on the opposite sideof the first electric motor and the second electric motor from theengine.

Further, in the foregoing vehicular drive system according to the firstaspect of the invention, the clutch may be arranged between the firstelectric motor and the second electric motor.

Further, in the foregoing vehicular drive system according to the firstaspect of the invention, the power transmitting means may be arrangedbetween the clutch and the second electric motor.

Next, a second aspect of the invention relates to a vehicular drivesystem including an engine, a first electric motor, a second electricmotor that is arranged on a second axis which is parallel with a firstaxis on which an output shaft of the engine is arranged, a transmissionthat is arranged on the second axis, a clutch that is arranged on thefirst axis and can selectively connect and disconnect the secondelectric motor and the transmission to and from the engine, thetransmission being arranged parallel to the engine and the clutch, andpower transmitting means that is arranged between the second electricmotor and the transmission and transmits power on the first axis to aninput shaft of the transmission.

According to this structure, the second electric motor and thetransmission are arranged on the second axis, which leaves some freespace on the first axis. Thus, arranging the first electric motor on thefirst axis enables the space to be used effectively, thereby enablingthe dimensions in the transverse direction, i.e., the axial direction,of the vehicular drive system to be shortened even more.

Further, in the foregoing vehicular drive system according to the secondaspect of the invention, the first electric motor may be arranged on thefirst axis.

Further, in the foregoing vehicular drive system according to the firstand second aspects of the invention, the transmission may include aplanetary gear set and a brake which selectively stops the rotation of arotating element of the planetary gear set, and the first or secondelectric motor arranged on the first axis and the brake may be arrangedoffset from one another in the axial direction.

The brake and the first and second electric motors are all elements thattypically have large radial dimensions on their respective shafts.Therefore, offsetting those elements which have large radial dimensionsin the axial direction on their respective shafts enables the shafts tobe closer together, which enables the longitudinal dimensions of thevehicular drive system to be made smaller.

Further, in the foregoing vehicular drive system according to the firstand second aspects of the invention, the power transmitting means may bearranged on the opposite side of the clutch from the engine.

Arranging the power transmitting means on the opposite side of theclutch from the engine results in the components being arranged in theorder of engine, clutch, and power transmitting means. As a result, thepower transmission path only doubles back once which is at the powertransmitting means, which is good for the transmission of power.

Further, in the foregoing vehicular drive system according to the firstand second aspects of the invention, the power transmitting means mayinclude a gear set.

Using a gear set as the power transmitting means between the first axisand the second axis obviates the need for a third axis to reverse therotation of the second axis, which is necessary when a belt is used asthe power transmitting means. As a result, the total number of shafts isable to be reduced, which enables the dimensions in the longitudinaldirection, i.e., the radial direction, of the drive system to beshortened even more.

The input shaft of the clutch and the output shaft of the engine may bedirectly connected or a pulsation absorbing damper (i.e., a pulsationreducing device) may be interposed between the two. Also, the clutch maybe provided on the opposite side of the first electric motor and thesecond electric motor from the engine on the first axis, i.e., on thedownstream side in the power transmission path from the first electricmotor and the second electric motor on the first axis. Alternatively,the clutch may be provided between the first electric motor and thesecond electric motor, or between the first electric motor and the powertransmitting means.

At least one of the first electric motor and the second electric motormay be a so-called motor-generator which has a power generatingfunction, or both may be motor-generators. An electric motor other thanthe first and second electric motors may also be provided.

When the second electric motor is arranged on the first axis, the powertransmitting means may be arranged between the clutch and the secondelectric motor. When the second electric motor is arranged on the secondaxis, the power transmitting means may be arranged between the secondelectric motor and the transmission. It is also possible to arrange thepower transmitting means at one end, in the axial direction, of thevehicular drive system irrespective of which axis the second electricmotor is arranged on.

The transmission is not limited so long as it can change the inputrotation speed by a plurality of speed ratios. For example, thetransmission can be a planetary gear type stepped transmission or atoroidal-type continuously variable transmission.

As the power transmitting means, a belt or chain may also be used, forexample.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and/or further objects, features and advantages of theinvention will become more apparent from the following description ofpreferred embodiment with reference to the accompanying drawings, inwhich like numerals are used to represent like elements and wherein:

FIG. 1 is a skeleton view of the structure of a vehicular drive systemto which the invention has been applied;

FIG. 2 is an alignment graph illustrating the operations of an automatictransmission shown in FIG. 1;

FIG. 3 is a clutch and brake application chart showing the relationshipbetween the speed of the automatic transmission shown in FIG. 1 and thecombination of operations of hydraulic friction apply devices necessaryto establish those speeds;

FIG. 4 is a view illustrating signals both input to and output from anECU for controlling the drive system shown in FIG. 1;

FIG. 5 is a simplified sectional view of a structure of the drive systemshown in FIG. 1;

FIG. 6 is a skeleton view of the structure of a vehicular drive systemaccording to a second exemplary embodiment of the invention;

FIG. 7 is a skeleton view of the structure of a vehicular drive systemaccording to a third exemplary embodiment of the invention; and

FIG. 8 is a skeleton view of the structure of a vehicular drive systemaccording to a fourth exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, exemplary embodiments of the invention will be described in detailwith reference to the accompanying drawings.

FIG. 1 is a skeleton view of the structure of a vehicular drive system(hereinafter simply referred to as “drive system”) 10 to which theinvention has been applied. This drive system 10 includes an engine 12and a transmission case 14 which is a non-rotating member mounted to avehicle body. The transmission case 14 houses a first motor-generatorMG1 which serves as a first electric motor, a second motor-generator MG2which serves as a second electric motor, a lock-up clutch Ci, a steppedautomatic transmission (hereinafter simply referred to as “automatictransmission”) 16 which serves as a transmission, and a counter gear set18 which serves as power transmitting means, and the like.

The first motor-generator MG1, the second motor-generator MG2, and thelock-up clutch Ci are all arranged in that order from the upstream sideof the power transmission path (i.e., from the engine 12 side) on afirst axis L1. Meanwhile, the automatic transmission 16 is arranged on asecond axis L2 which is parallel to the first axis L1.

A crankshaft 20, i.e., the output shaft of the engine 12, is alsoarranged on the first axis L1. A rotating shaft 22 of the firstmotor-generator MG1 is connected to the crankshaft 20 via a flywheel 62and a transmitting member 64 or a damper 65, not shown in FIG. 1 (seeFIG. 5). Thus, when the rotating shaft 22 of the first motor-generatorMG1 is directly connected to the crankshaft 20 of the engine 12 withoutthe use of a belt or the like, the crankshaft 20 is directly rotated bythe rotating shaft 22 of the first motor-generator MG1. Therefore, theengine is able to be started up easily even when a large amount of forceis required at engine startup, such as when the engine 12 is cold.Further, this rotating shaft 22 also functions as an input shaft of thelock-up clutch Ci.

The lock-up clutch Ci is, for example, a multiple disc type hydraulicfriction apply device in which the discs are frictionally engaged witheach other by a hydraulic cylinder. This lock-up clutch Ci includes afriction plate 26 which rotates together with the input shaft which isthe prime mover shaft, i.e., the rotating shaft 22, and friction plates30 which rotate together with a clutch drum 28 which is a rotated body.The clutch drum 28 is connected to a rotor shaft 32 of the secondmotor-generator MG2. This lock-up clutch Ci selectively connects anddisconnects the first motor-generator MG1 and the automatic transmission16 to and from the engine 12. Accordingly, the lock-up clutch Ci alsofunctions as an input clutch that inputs power from the engine 12 andthe first motor-generator MG1 to the automatic transmission 16.

The counter gear set 18 includes a drive gear 34 and a driven gear 36which are in mesh with each other. The drive gear 34 is provided on theoutput shaft 38 of the lock-up clutch Ci so as not to be able to rotatewith respect to the output shaft 38, and is on the opposite side of thelock-up clutch Ci from the engine 12 on the first axis L1, i.e., on thedownstream side of the lock-up clutch Ci on the first axis L1 in thepower transmission path. The driven gear 36 is provided on one end ofthe input shaft 40 of the automatic transmission 16 on the second axisL2, so as not to be able to rotate with respect to the input shaft 40.This counter gear set 18 transmits rotation from the rotor shaft 32 ofthe second motor-generator MG2, which is a rotating shaft on the firstaxis L1, to the input shaft 40 of the automatic transmission 16 providedon the second axis L2. Because the counter gear set 18 makes up one endof the drive system 10, the lock-up clutch Ci, which is arranged next tothe counter gear set 18 is also close to the transmission case 14.Therefore, hydraulic fluid can be supplied to the lock-up clutch Ci viathe transmission case 14 or a support member fitted in the transmissioncase 14. Providing hydraulic fluid via the transmission case 14 or thesupport member in this way enables the oil supply path to be simplifiedcompared with when hydraulic fluid is supplied via a shaft.

The automatic transmission 16 is provided to the right of the countergear set 18 on the second axis L2 in the drawing, i.e., on the same sideof the counter gear set 18 as is the engine 12. Therefore, the automatictransmission 16 is arranged in a position in which it substantiallyoverlaps in the axial direction with the engine 12, the firstmotor-generator MG1, the second motor-generator MG2, and the lock-upclutch Ci on the first axis L1. That is, the automatic transmission 16is arranged parallel with the engine 12, the first motor-generator MG1,the second motor-generator MG2, and the lock-up clutch Ci on the firstaxis L1.

This automatic transmission 16 includes a first transmitting portion 44and a second transmitting portion 50. The main component of the firsttransmitting portion 44 is a first planetary gear set 42. The maincomponents of the second transmitting portion 50 are a second planetarygear set 46 and a third planetary gear set 48.

The first planetary gear set 42 is a double pinion type planetary gearset and includes a sun gear S1, a plurality of sets of pinions gears P1which are in mesh with each other, a carrier CA1 which rotatably andrevolvably supports the pinion gears P1, and a ring gear R1 which is inmesh with the sun gear S1 via the pinion gears P1. The carrier CA1 isconnected to, and rotatably driven by, the input shaft 40, while the sungear S1 is integrally fixed to the transmission case 14 so as not to beable to rotate. The ring gear R1 functions as an intermediate outputmember and slows the rotation input from the input shaft 40 andtransmits it to the second transmitting portion 50. In this exemplaryembodiment, there is a first intermediate output path PA1 whichtransmits rotation from the input shaft 40 to the second transmittingportion 50 without changing the rotation speed. This path transmitsrotation at a predetermined constant speed ratio (=1.0). This firstintermediate output path PA1 includes a direct path PA1 a and anindirect path PA1 b. The direct path PA1 a transmits rotation from theinput shaft 40 to the second transmitting portion 50 without passingthrough the first planetary gear set 42. The indirect path PA1 btransmits rotation from the input shaft 40 to the second transmittingportion 50 via the carrier CA1 of the first planetary gear set 42. Thereis also a second intermediate output path PA2 which transmits rotationfrom the input shaft 40 to the second transmitting portion 50 via thecarrier CA1, the pinion gears P1 arranged on the carrier CA1, and thering gear R1. This path slows the rotation input from the input shaft 40and transmits it at a larger speed ratio (>1.0) than does the firstintermediate output path PA1.

The second planetary gear set 46 is a single pinion type planetary gearset which includes a sun gear S2, a pinion gear P2, a carrier CA2 whichrotatably and revolvably supports that pinion gear P2, and a ring gearR2 which is in mesh with the sun gear S2 via the pinion gear P2. Thethird planetary gear set 48 is a double pinion type planetary gear setand includes a sun gear S3, a plurality of sets of pinion gears P2 andP3 which are in mesh with each other, a carrier CA3 which rotatably andrevolvably supports those pinion gears P2 and P3, and a ring gear R3which is in mesh with the sun gear S3 via the pinion gears P2 and P3.

In the second planetary gear set 46 and the third planetary gear set 48,four rotating elements RM1, RM2, RM3, and RM4 are formed by common useof the carriers CA2 and CA3 which rotatably support the pinion gear P2,and the ring gears R2 and R3. That is, the sun gear S2 of the secondplanetary gear set 46 serves as the first rotating element RM1, thecarrier CA2 of the second planetary gear set 46 and the carrier CA3 ofthe third planetary gear set 48 are integrally connected together andserves as the second rotating element RM2, the ring gear R2 of thesecond planetary gear set 46 and the ring gear R3 of the third planetarygear set 48 are integrally connected together and serve as the thirdrotating element RM3, and the sun gear S3 of the third planetary gearset 48 serves as the fourth rotating element RM4.

The first rotating element RM1 (i.e., the sun gear S2) is selectivelyheld to the transmission case 14 by a first brake B1, which prevents itfrom rotating. The first rotating element RM1 (i.e., the sun gear S2) isalso selectively connected to the ring gear R1 of the first planetarygear set 42, i.e., the intermediate output member, via a third clutch C3(i.e., the second intermediate output path PA2). The first rotatingelement RM1 (i.e., the sun gear S2) is further selectively connected tothe carrier CA1 of the first planetary gear set 42 via a fourth clutchC4 (i.e., the indirect path PA1 b of the first intermediate output pathPA1). The second rotating element RM2 (i.e., the carriers CA2 and CA3)is selectively held to the transmission case 14 by a second brake B2,which prevents it from rotating, and is also selectively connected tothe input shaft 40 via a second clutch C2 (i.e., the direct path PA1 aof the intermediate output path PA1). The third rotating element RM3(i.e., the ring gears R2 and R3) is integrally connected to an outputshaft 52 of the automatic transmission 16 and outputs rotation. Thefourth rotating element RM4 (i.e., the sun gear S3) is connected to thering gear R1 via a first clutch C1. The brakes B1 and B2 and theclutches C1 to C4 are all multiple disc hydraulic friction apply devicesthat are frictionally engaged by means of a hydraulic cylinder.

The output shaft 52 of the automatic transmission 16 is provided on thesame end side of the drive system 10 as the engine 12 and has a drivepinion gear 54 which is unable to rotate relative to the output shaft52. This drive pinion gear 54 is in mesh with a ring gear 58 thatrotates together with a differential gear unit 56. With the vehiculardrive system 10 having this kind of structure, driving force generatedby rotation of the engine, the first motor-generator MG1, and the secondmotor-generator MG2, which are all arranged on the first axis L1, istransmitted to the second axis L2 by the counter gear set 18 where it issent in the opposite direction, axially, i.e., back toward the sidewhere the engine 12 is located, and output from the output shaft 52 ofthe automatic transmission 16 provided on the same end side, in theaxial direction, as the engine 12.

FIG. 2 is an alignment graph that is able to illustrate, with straightlines, the rotation speed of each rotating element of the firsttransmitting portion 44 and the second transmitting portion 50. Thelower horizontal line represents a rotation speed of “0” while the upperhorizontal line represents a rotation speed of “1.0”, i.e., a rotationspeed equal to that of the input shaft 40. Also, the vertical lines onthe first transmitting portion 44 side represent, in order from left toright, the sun gear S1, the ring gear R1, and the carrier CA1. Thedistances between those vertical lines are set according to the gearratio ρ1 (=the number of teeth on the sun gear S1/the number of teeth onthe ring gear R1) of the first planetary gear set 42. In FIG. 2, thespeed ratio ρ1 equals 0.463, for example. The four vertical lines on thesecond transmitting portion 50 side represent, in order from left toright, the first rotating element RM1 (i.e., the sun gear S2), thesecond rotating element RM2 (i.e., the carrier CA2 and the carrier CA3),the third rotating element RM3 (i.e., the ring gear R2 and the ring gearR3), and the fourth rotating element RM4 (i.e., the sun gear S3). Thedistances between those vertical lines are set according to the speedratio ρ2 of the second planetary gear set 46 and the speed ratio ρ3 ofthe third planetary gear set 48. In FIG. 2, ρ2 equals 0.463 and ρ3equals 0.415, for example.

As can be seen from the alignment graph, eight forward speeds, i.e., afirst forward speed “1st” through an eighth forward speed “8th”, and tworeverse speeds, i.e., a first reverse speed “Rev1” and a second reversespeed “Rev2” can be established depending on the operative state(applied or released) of the clutches C1 to C4 and the brakes B1 and B2.

FIG. 3 is a clutch and brake application chart showing the relationshipbetween the apply devices when each speed is established and the speedratio of each speed. In the drawing, a circle indicates an applied stateand the absence of a circle indicates a released state. The speed ratioof each speed is set appropriately by the speed ratio ρ1 of the firstplanetary gear set 42, the speed ratio ρ2 of the second planetary gearset 46, and the speed ratio ρ3 of the third planetary gear set 48. Ifρ1=0.463, ρ2=0.463, and ρ3=0.415 as shown in FIG. 3, then the value ofthe speed ratio steps (i.e., the ratio of the speed ratios between thespeeds) is generally appropriate, and the total speed ratio range(=4.495/0.683) is large, around 6.581. Further, the speed ratios of thereverse speeds “Rev1” and “Rev2” are also suitable. As a result,appropriate overall speed ratio characteristics are able to be obtained.As shown in FIG. 3, the automatic transmission 16 is able to realize alarge speed ratio range with appropriate speed ratio steps. Furthermore,speeds can be shifted by simply changing the operative state of any twoof the four clutches C1 to C4 and the two brakes B1 and B2. As a result,shift control is simplified and shift shock is able to be suppressed.

FIG. 4 is a view illustrating signals both input to and output from anelectronic control unit (ECU) 60 for controlling the drive system 10according to this exemplary embodiment. The ECU 60 includes a so-calledmicrocomputer that includes a CPU, ROM, RAM, and an input/outputinterface and the like. The ECU 60 runs the vehicle in a plurality ofoperating modes in which the engine 12 and the motor-generators MG1 andMG2 are in different operating states, by executing output control ofthe engine 12, shift control of the automatic transmission 16, andpowering/regenerating control of the motor-generators MG1 and MG2, andthe like by performing signal processing according to a program storedbeforehand in the ROM while using the temporary storage function of theRAM.

Various signals output from the various sensors and switches shown inFIG. 4 are input to the ECU 60. Examples of these signals include asignal indicative of the engine coolant temperature, a signal indicativeof the shift lever position, a signal indicative of the engine speed NE,i.e., the rotation speed of the engine 12, Decel1 and Decel2 signalsindicative of target values of vehicle deceleration bypowering/regenerating control of the engine brake and themotor-generators MG1 and MG2, i.e., signals directing an increase in thetarget deceleration, Can-Decel1 and Can-Decel2 signals directing adecrease in the target deceleration, a signal directing a decelerationcontrol mode (i.e., E-mode) for controlling the target deceleration, anair conditioner signal indicative of operation of an air conditioner, avehicle speed signal which corresponds to the rotation speed of theoutput shaft 52, an AT fluid temperature signal indicative of thehydraulic fluid in the automatic transmission 16, a signal indicative ofan emergency brake operation, and a signal indicative of a foot brakeoperation. Other examples of signals input to the ECU 60 include acatalyst temperature signal indicative of the temperature of a catalyst,an accelerator opening amount signal indicative of the operating amountof an accelerator pedal, a cam angle signal, a snow mode setting signalindicative of a snow mode setting, an acceleration signal indicative offorward/backward acceleration of the vehicle, an auto cruise signalindicative of auto cruise running, a signal indicative of a rotationspeed NMG1 of the first motor-generator MG1, and a signal indicative ofa rotation speed NMG2 of the second motor-generator MG2.

In addition, various signals are also output from the ECU 60. Examplesof these signals include a drive signal to a throttle actuator whichcontrols the opening amount of a throttle valve, a boost pressure adjustsignal for adjusting boost pressure, an electric air conditioner drivesignal for operating an electric air conditioner, an ignition signalwhich directs the ignition timing of the engine 12, a command signalwhich directs operation of the motor-generators MG1 and MG2, a shiftlever position (i.e., operating position) indication signal foroperating a shift indicator, a speed ratio indication signal forindicating the speed ratio, a snow mode indication signal for indicatingwhen the snow mode is set, an ABS activation signal for activating anABS actuator which prevents the wheels of the vehicle from slippingduring braking, an E-mode indication signal which indicates that theE-mode is selected, a valve command signal which activates anelectromagnetic valve in the hydraulic pressure control circuit forcontrolling a hydraulic pressure actuator of hydraulic frictionengagement devices provided in the transmission 16 and the lock-upclutch Ci, a drive command signal for activating an electric hydraulicpump which is the source of hydraulic pressure in the hydraulic pressurecontrol circuit, a signal for driving an electric heater, and a signalto a cruise control computer.

The plurality of operating modes which are controlled by the ECU 60includes an engine running mode, an engine plus motor running mode, amotor running mode, and a deceleration control mode. In the enginerunning mode, the lock-up clutch Ci is applied to connect the engine 12,and the vehicle is run by driving force generated by the engine 12. Whennot all of the power generated by the engine 12 is being used to drivethe vehicle, for example, the first electric motor MG1 can be controlledto regenerate that power as necessary and use it to charge the battery.In the engine plus motor running mode, the lock-up clutch Ci is appliedto connect the engine 12, and the vehicle is run by the driving forcegenerated by both the engine 12 and the second electric motor MG2. Inthe motor running mode, the lock-up clutch Ci is released to disconnectthe engine 12, and the vehicle is run by the driving force generated bythe second electric motor MG2. When the state-of-charge SOC of thebattery is low, for example, the engine 12 is operated as necessary andthe first electric motor MG1 is controlled to regenerate power andcharge the battery. In the deceleration control mode, the lock-up clutchCi is applied to connect the engine 12 and the supply of fuel to theengine 12 is stopped by a fuel cut to induce engine braking, while thesecond electric motor MG2 is controlled to either produce or regeneratepower, thereby generating a predetermined power source brake. The firstelectric motor MG1 can also be used to adjust the power source brake byalso being controlled to either produce or regenerate power, just likethe second electric motor MG2.

FIG. 5 is a simplified sectional view of a structure of the drive system10. As shown in FIG. 5, the transmission case 14 has a first case 14 aand a second case 14 b which are joined together with a bolt, not shown.The first case 14 a houses the first motor-generator MG1 and the secondmotor-generator MG2 and the like, while the second case houses theflywheel 62, the transmitting member 64, and the damper 65 and the like.The second case 14 b is integrated with the engine 12.

Housed in the first case 14 a, in order from the side nearest the engine12, are a first support wall 66, a second support wall 68, and a thirdsupport wall 70. These first, second, and third support walls 66, 68,and 70 have a bell and spigot configuration with respect to the firstcase 14 a. That is, the outer peripheral surfaces of the first andsecond support walls 66 and 68 abut against a first abutting surface 72which is formed on, and parallel in the axial direction with, the innerperipheral surface of the first case 14 a. The outer peripheral surfaceof the third support wall 70 abuts against a second abutting surface 74which is formed farther to the rear of the first abutting surface 72 inthe first case 14 a and is parallel in the axial direction, just likethe first abutting surface 72, but which has a smaller diameter thandoes the first abutting surface 72. When not fixed in place by bolts 76and 78, the support walls 66, 68, and 70 can slide with respect to thefirst case 14 a. The positions, in the radial direction, of the firstthrough the third support walls 66, 68, and 70 are determined by thisbell and spigot configuration.

The first support wall 66 is a generally disc-shaped member. The secondsupport wall 68, on the other hand, includes an outer peripheral sidecylindrical portion 68 a which abuts against the first abutting surface72, a connecting portion 68 b which is connected at one end to the endof the outer peripheral side cylindrical portion 68 a on the secondmotor-generator MG2 side and which extends inward in the radialdirection, and a shaft portion 68 c which is connected to the other end,i.e., the inner peripheral end, of the connecting portion 68 b andextends in the direction opposite that of the outer peripheral sidecylindrical portion 68 a. Further, the third support wall 70 includes anouter peripheral side cylindrical portion 70 a which abuts against thesecond abutting surface 74, a connecting portion 70 b which is connectedto the end of the outer peripheral side cylindrical portion 70 a on theside opposite the first motor-generator MG1 and which extends inward inthe radial direction, and a shaft portion 70 c which is connected to theother end, i.e., the inner peripheral end, of the connecting portion 70b and extends in the same direction as the outer peripheral sidecylindrical portion 70 a.

Also, the first case 14 a has a first radial surface 80 in the radialdirection which connects the first abutting surface 72 and the secondabutting surface 74 together, and a second radial surface 82 whichextends toward the inner radial side from the other end of the secondabutting surface 74. The position, in the axial direction, of the secondsupport wall 68 is determined by the second support wall 68 abuttingagainst the first radial surface 80. Similarly, the position, in theaxial direction, of the third support wall 70 is determined by the thirdsupport wall 70 abutting against the second radial surface 82. Theposition, in the axial direction, of the first support wall 66 isdetermined by the first support wall 66 abutting against a side surfaceof the second support wall 68 that is opposite the side surface of thesecond support wall 68 that abuts against the first radial surface 80.The first support wall 66 and the second support wall 68 are fixed tothe first case 14 a by the bolt 76 which passes through, in the axialdirection, the first support wall 66 and the outer peripheral sidecylindrical portion 68 a of the second support wall 68 and screws intothe first case 14 a. Similarly, the third support wall 70 is fixed tothe first case 14 a by the bolt 78 which passes through, in the axialdirection, the outer peripheral side cylindrical portion 70 a of thethird support wall 70 and screws into the first case 14 a.

The first support wall 66 and the second support wall 68 define a firsthousing chamber 84, while the second support wall 68, the third supportwall 70, and the first case 14 a define a second housing chamber 86. Thefirst housing chamber 84 houses the first motor-generator MG1, while thesecond housing chamber 86 houses the lock-up clutch Ci on the thirdsupport wall 70 side and the second motor-generator MG2 on the secondsupport wall 68 side. An oil pump for supplying hydraulic fluid to thelock-up clutch Ci can be used as the third support wall 70, whichenables the number of support walls to be reduced as compared to ifanother support wall were provided.

The rotating shaft rotating shaft 22 of the first motor-generator MG1includes a rotor shaft 22 a and an input shaft 22 b which is arrangedinside the rotor shaft 22 a but which does not contact the rotor shaft22 a. The rotational driving force of the rotor 88 of the firstmotor-generator MG1 is input from the rotor shaft 22 a to the inputshaft 22 b via the transmitting member 64 which is fitted with a spline90 to the engine 12 side end of the rotor shaft 22 a, and the damper 65which is integrated with the transmitting member 64 by a bolt 92 andfitted to the input shaft 22 b with a spline 94.

The transmitting member 64 and the damper 65 are fixed to an outerperipheral portion of the flywheel 62 by the bolt 92. Also, the flywheel62 is fixed at an inner peripheral end portion thereof to the crankshaft20 by a bolt 98. The transmitting member 64, the damper 65, and theflywheel 62 are all members which are housed in the second case 14 b,while the rotor shaft 22 a, which is fitted to the transmitting member64, and the input shaft 22 b, which is fitted to the damper 65, arehoused in the first case 14 a. The transmitting member 64 and the rotorshaft 22 a are fitted together with the spline 90 and the damper 65 andthe input shaft 22 b are fitted together with the spline 94, whichfacilitates assembly of the first case 14 a to the second case 14 b.

The rotor shaft 22 a is supported at one end by the first support wall66 via a bearing 100 provided at the inner peripheral surface of thefirst support wall 66, and at the other end by the second support wall68 via a bearing 102 provided at the inner peripheral surface of theconnecting portion 68 b of the second support wall 68. Supporting therotor shaft 22 a by the first support wall 66 and the second supportwall 68 in this way makes the first housing chamber 84 a closed space.As a result, once the rotor shaft 22 a is assembled, foreign matter isprevented from adhering to the rotor 88 inside the first housing chamber84 even before the first case 14 a and the second case 14 b are joinedtogether. Furthermore, the positions, in the radial direction, of thefirst support wall 66 and the second support wall 68 which support therotor shaft 22 a at both ends are determined by the first support wall66 and the second support wall 68 abutting against the first abuttingsurface 72 of the first case 14 a. That is, the positions, in the radialdirection, of the first support wall 66 and the second support wall 68are determined with reference to the same surface of the same member.Therefore, the axial precision of the rotor shaft 22 a that is supportedby the first support wall 66 and the second support wall 68 is improvedcompared with a case in which the positions, in the radial direction, ofthe first support wall 66 and the second support wall 68 are determinedwith reference to different members.

Moreover, seal members 104 and 106 are provided adjacent to, but onopposite sides of, the bearings 100 and 102, between the innerperipheral surface of the first support wall 66 and the rotor shaft 22a, and between the inner peripheral surface of the connecting portion 68b of the second support wall 68 and the rotor shaft 22 a, respectively.These seal members 104 and 106 seal off the first housing chamber 84. InFIG. 5, the bearing 100 and the seal member 104 are separate members, asare the bearing 102 and the seal member 106. Alternatively, however, thebearing 100 and the seal member 104 may be integrated together, and thebearing 102 and the seal member 106 may be similar.

The input shaft 22 b extends through the rotor shaft 22 a and the shaftportion 68 c of the second support wall 68. This input shaft 22 b issupported by the second support wall 68 via a pair of bearings 108 and110, one of which is provided near one side, in the axial direction, ofthe shaft portion 68 c of the second support wall 68 and the other ofwhich is provided near the other side, in the axial direction, of theshaft portion 68 c of the second support wall 68. Furthermore, a sealmember 112 is provided between the input shaft 22 b and the shaftportion 68 c of the second support wall 68 toward the engine 12 side ofthe bearing 108 which is the bearing, from among the pair of bearings108 and 110, that is on the engine 12 side. This seal member 112 sealsoff the second housing chamber 86.

In this way, the first housing chamber 84 and the second housing chamber86 are sealed spaces so even if water enters between the first case 14 aand the second case 14 b, the first motor-generator MG1 and the secondmotor-generator MG2, which are electrical components, will not get wet.

The rotor shaft 32 of the second motor-generator MG2 is supported atboth ends by the shaft portion 68 c of the second support wall 68 via apair of bearings 114 and 116 which are arranged at the outer peripheralsurface of that shaft portion 68 c. In this way, the second support wall68 supports both the input shaft 22 b and one end portion of the rotorshaft 22 a of the first motor-generator MG1, which reduces the number ofsupport walls compared to a case in which support walls are providedseparately to support these shafts 32, 22 a, and 22 b.

The clutch drum 28 is fixed to one end of the rotor shaft 32. The innerperipheral end of a flange portion 28 a of the clutch drum 28 is fittedby a spline 118 to the output shaft 38 of the lock-up clutch Ci. Aneedle bearing 120 is provided between the output shaft 38 and a shaftportion 70 c of the third support member 70.

According to the exemplary embodiment described above, the secondmotor-generator MG2 and the lock-up clutch Ci are provided on the firstaxis L1 on which the crankshaft 20 of the engine 12 is arranged.Furthermore, the automatic transmission 16, which has long dimensions inthe axial direction, is arranged on the second axis L2 which isdifferent from the first axis L1, and the engine 12 and the lock-upclutch Ci on the first axis L1 are arranged parallel to the automatictransmission 16 on the second axis L2. As a result, the dimensions inthe transverse direction, i.e., the dimensions in the axial direction,of the vehicular drive system 10 are able to be shortened.

Moreover, the first motor-generator MG1 is also arranged on the firstaxis L1 of a different shaft than that of the automatic transmission 16which is long in the axial direction. As a result, the dimensions in thetransverse direction, i.e., the dimensions in the axial direction, ofthe vehicular drive system 10 are able to be shortened even more.

Also according to this exemplary embodiment, the engine 12, lock-upclutch Ci, and counter gear set 18, are arranged in that order from theupstream side of the power transmission path. As a result, the powertransmission path only doubles back once, which is at the counter gearset 18, resulting in good power transmission.

Also according to this exemplary embodiment, the counter gear set 18 isused as the power transmitting means so a third axis to reverse therotation of the second axis L2, such as when a belt is used as the powertransmitting means, is unnecessary. As a result, the total number ofshafts is able to be reduced, which enables the dimensions in thelongitudinal direction, i.e., the radial direction, of the drive system10 to be shortened.

Next, a second exemplary embodiment of the invention will be described.In the following description, members in the second exemplary embodimentthat are the same as those in the first exemplary embodiment are denotedwith the same reference numerals and characters, and descriptionsthereof are omitted.

FIG. 6 is a skeleton view of the structure of a vehicular drive system(hereinafter simply referred to as “drive system”) 130 according to thesecond exemplary embodiment of the invention. The only differencebetween the drive system 130 and the drive system 10 of the firstexemplary embodiment is that the positions of the second motor-generatorMG2 and the lock-up clutch Ci are reversed. That is, in the drive system130 according to the second exemplary embodiment, the order of thecomponents on the first axis L1 from the upstream side of the powertransmission path is as follows: the engine 12, the firstmotor-generator MG1, the lock-up clutch Ci, the second motor-generatorMG2, and the drive gear 34 of the counter gear set 18.

The output shaft 38 of the lock-up clutch Ci and the rotor shaft 32 ofthe second motor-generator MG2 are connected in a manner such that theyare unable to rotate with respect to one another. The drive gear 34 ofthe counter gear set 18 is provided on the rotor shaft 32 so as not tobe able to rotate with respect to the rotor shaft 32.

Thus, because the drive system 130 according to the second exemplaryembodiment differs from the drive system 10 according to the firstexemplary embodiment only in that the positions of the secondmotor-generator MG2 and the lock-up clutch Ci are reversed, theadvantages obtained by the first exemplary embodiment are also able tobe obtained by this second exemplary embodiment, that is, the dimensionsin the transverse direction, i.e., the axial direction, of the drivesystem 130 can be shortened, good power transmission can be achieved,and the dimensions in the longitudinal direction, i.e., the radialdirection, of the drive system 130 can be shortened. Just as disclosedin US Patent Application Publication No. 2003/0127262A 1, arranging thelock-up clutch Ci on the inner peripheral side of the stator of thesecond motor-generator MG2 enables the dimensions in the transversedirection, i.e., the axial direction, to be shortened even more.

Next, a third exemplary embodiment of the invention will be described.FIG. 7 is a skeleton view of the structure of a vehicular drive system(hereinafter simply referred to as “drive system”) 140 according to thethird exemplary embodiment of the invention. The drive system 140differs from the drive system 10 of the first exemplary embodiment inthat the positional relationships between the lock-up clutch Ci, thedrive gear 34, and the second motor-generator MG2 on the first axis L1are different. That is, in the drive system 140 according to the thirdexemplary embodiment, the order of the components on the first axis L1from the engine 12 side is as follows: the engine 12, the firstmotor-generator MG1, the lock-up clutch Ci, the drive gear 34, and thesecond motor-generator MG2. Therefore, in this exemplary embodiment itis the second motor-generator MG2 that is provided at the opposite endfrom the engine 12 on the first axis L1.

The output shaft 38 of the lock-up clutch Ci and the rotor shaft 32 ofthe second motor-generator MG2 are connected in a manner such that theyare unable to rotate with respect to one another. The drive gear 34 isprovided on either the output shaft 38 or the rotor shaft 32 so as to benon-rotatable with respect thereto.

As described above, according to this exemplary embodiment, it is thesecond motor-generator MG2 that is provided on the opposite end from theengine 12 on the first axis L1, so the drive gear 34 is positionedfarther on the engine 12 side than it is in the first and secondexemplary embodiments. Meanwhile, the same automatic transmission 16 asin the first and second exemplary embodiments is arranged on the secondaxis L2 on the same side of the counter gear set 18 as it is in thefirst and second exemplary embodiments. Therefore, according to thisexemplary embodiment, the first motor-generator MG1 and the secondmotor-generator MG2, which are arranged on the first axis L1, are offsetin the axial direction with respect to the first brake B1 and the secondbrake B2 on the second axis L2. The motor-generators MG1 and MG2 and thebrakes B1 and B2 are all elements that have large radial dimensions.Offsetting these elements in the axial direction therefore enables thedimensions in the radial direction, i.e., the longitudinal direction, ofthe drive system 140 to be shortened even more.

Also, just as in the drive system 10 according to the first exemplaryembodiment, the drive system 140 according to this exemplary embodimenthas the first motor-generator MG1, the second motor-generator MG2, andthe lock-up clutch Ci arranged on the first axis L1 on which thecrankshaft 20 of the engine 12 are arranged. Further, the automatictransmission 16, which has large radial dimensions, is arranged on thesecond axis L2 which is a different axis than the first axis L1 on whichthe first motor-generator MG1, the second motor-generator MG2, and thelock-up clutch Ci are arranged. Moreover, the engine 12 and the lock-upclutch Ci on the first axis L1 are parallel with the automatictransmission 16 on the second axis L2. As a result of this structure,the dimensions in the transverse direction, i.e., the axial direction,of the drive system 140 are able to be shortened. Also, the counter gearset 18 is used as the power transmitting means so the total number ofshafts is able to be reduced. As a result, the dimensions in thelongitudinal direction, i.e., the radial direction, of the drive system140 are able to be shortened.

Next, a fourth exemplary embodiment of the invention will be described.FIG. 8 is a skeleton view of the structure of a vehicular drive system(hereinafter simply referred to as “drive system”) 150 according to thefourth exemplary embodiment of the invention. The drive system 150differs from the drive system 140 of the third exemplary embodiment onlyin that, in the third exemplary embodiment the second motor-generatorMG2 is arranged at the opposite end from the engine 12 on the first axisL1, whereas in the fourth exemplary embodiment the secondmotor-generator MG2 is arranged at the opposite end from the drivepinion gear 54 on the second axis L2.

That is, in the drive system 150 according to the fourth exemplaryembodiment, only the engine 12, the first motor-generator MG1, thelock-up clutch Ci, and the drive gear 34 are arranged in that order fromthe engine side 12 on the first axis L1, which makes the structure onthe first axis L1 extremely simple. On the other hand, the secondmotor-generator MG2, the driven gear 36, the automatic transmission 16,and the drive pinion gear 54 are arranged, in that order, on the secondaxis L2. The rotor shaft 32 of the second motor-generator MG2 and theinput shaft 40 of the automatic transmission 16 are connected togetherso as not to be able to rotate relative one another, and the driven gear36 is provided on either the rotor shaft 32 or the input shaft 40 so asnot to be able to rotate relative thereto.

In the drive system 150, the structure to the engine 12 side of thecounter gear set 18 is the same as that of the drive system 140according to the third exemplary embodiment, with the firstmotor-generator MG1 on the first axis L1 being offset in the axialdirection with respect to the first brake B1 and the second brake B2 onthe second axis L2. The second motor-generator MG2 arranged on thesecond axis L2 is also offset in the axial direction with respect to theposition of the first motor-generator MG1 on the first axis L1.Therefore, this exemplary embodiment also enables the longitudinaldimensions of the drive system 150 to be shortened.

Moreover, in the drive system 150 according to this exemplaryembodiment, the first motor-generator MG1 and the lock-up clutch Ci arearranged on the first axis L1, on which is arranged the crankshaft 20 ofthe engine 12. Further, the automatic transmission 16, which has largeradial dimensions, is arranged on the second axis L2 which is adifferent axis than the first axis L1 on which the first motor-generatorMG1 and the lock-up clutch Ci are arranged. Moreover, the engine 12 andthe lock-up clutch Ci on the first axis L1 are parallel with theautomatic transmission 16 on the second axis L2. As a result of thisstructure, the dimensions in the transverse direction, i.e., the axialdirection, of the drive system 150 are able to be shortened. Also, thecounter gear set 18 is used as the power transmitting means so the totalnumber of shafts is able to be reduced. As a result, the dimensions inthe longitudinal direction, i.e., the radial direction, of the drivesystem 150 are able to be shortened.

Although the invention has been described herein with reference tospecific embodiments, many modifications and variations therein willreadily occur to those skilled in the art. Accordingly, all suchvariations and modifications are included within the intended scope ofthe invention.

1.-9. (canceled)
 10. A vehicular drive system, comprising: an engine; afirst electric motor; a second electric motor that is arranged on asecond axis which is parallel with a first axis on which an output shaftof the engine is arranged; a transmission that is arranged on the secondaxis; a clutch that is arranged on the first axis and can selectivelyconnect and disconnect the second electric motor and the transmission toand from the engine, the transmission being arranged parallel to theengine and the clutch; and a power transmitting mechanism that isarranged between the second electric motor and the transmission andtransmits power on the first axis to an input shaft of the transmission.11. The vehicular drive system according to claim 10, wherein the firstelectric motor is arranged on the first axis.
 12. The vehicular drivesystem according to claim 11, wherein the transmission includes aplanetary gear set and a brake which selectively stops the rotation of arotating element of the planetary gear set, and wherein the firstelectric motor and the brake are arranged offset from one another in theaxial direction.
 13. The vehicular drive system according to claim 10,wherein the power transmitting mechanism is arranged on the oppositeside of the clutch from the engine.
 14. The vehicular drive systemaccording to claim 10, wherein the power transmitting mechanism is agear set.